AJP - Heart and Circulatory Physiology, Vol 238, Issue 3 365-H372, Copyright © 1980 by American Physiological Society
Blood pressure, plasma catecholamines, and sympathetic outflow in pithed SHR and WKY rats
I. Yamaguchi and I. J. Kopin
After destruction, by pithing, of the central nervous system, the blood
pressure (BP) of the spontaneously hypertensive (SHR) rat falls, but
remains higher than in the pithed normotensive (WKY) rat. At all ages
examined, stimulation of the sympathetic outflow evoked greater increases
in BP of pithed SHR rats, but the increases in plasma catecholamines were
similar in the two strains. The BP increase evoked by administered
norepinephrine was greater in old SHR than in old WKY rats, but this
increased response was not found in young animals. Both young and old SHR
rats, however, were more sensitive than WKY rats to the pressor effects of
epinephrine. Results of selective pharmacologic blockade of cardiac or
vascular beta-adrenoceptors suggest that a smaller vasodilator response in
young SHR rats to the beta-adrenergic effects of epinephrine is responsible
for the greater pressor response than in WKY rats. This factor diminishes
in older SHR rats in which, as suggested by Folkow, structural changes in
the resistance blood vessel diameter may account for the enhanced pressor
responsivity of SHR rats.
